1. Field of the Invention
The present invention relates to an image processor and an image processing method, and more particularly to an image processor applicable to a decoder such as a video decoder which outputs video signals and inserts information directly into an image.
2. Description of the Background Art
In Japan, teletext broadcasting has been received by a monitor with a video decoder or a dedicated unit for receiving teletext broadcasting. When normal video is displayed, the monitor displays image data but not teletext data that is treated like a closed caption. The monitor displays teletext data only when the user requests it. More specifically, the monitor receives a signal that has teletext data inserted in a predetermined position during the vertical blanking period of the video signal and extracts the teletext data from the predetermined position for display on the monitor.
Data services using a similar technology is not limited to Japan. For example, the Federal Communications Commission (FCC) has proposed the standard for closed captions. The Electric Industry Association (EIA)-608 is one of related guideline standards. This standard recommends the data service for the 21st line. The closed caption, one of the technologies developed by the National Captioning Institute (NCI), is employed in the United States as the formal teletext method.
In practice, the data services using closed captions provided as a function of an image processor are executed by special hardware composed of many devices which write data into predetermined positions and read it back for transmission and by software controlled, for example, by the central processing unit (CPU).
An image processor or an image display that processes image data is required to process a large amount of data speedily. To satisfy this processing need, a Synchronous Dynamic Random Access Memory (SDRAM) is usually used as a frame memory.
An image processor is required to provide an enhanced data provision service through useful functions and speedy processing to differentiate it from similar image processors. An image processor is also required to provide at least the closed caption function to give more advantages and to provide new functions at lower costs. These requirements, in turn, require that the closed caption function be implemented in a simpler configuration.